It is well known that when a silver halide color photographic material is subjected to color development, couplers present therein undergo reaction with oxidized aromatic primary amine type color developing agents to produce indophenol dyes, indoaniline dyes, indamine dyes, azomethine dyes, phenoxazine dyes, phenazine dyes, or analogues thereof, whereby color images are formed. In this method, the subtractive color process is generally employed for color reproduction, and silver halide emulsions sensitized selectively to blue light, green light, and red light, respectively, and yellow-, magenta-, and cyan-dye-forming agents which bear a complementary color relationship to their corresponding emulsions are used in combination. In order to form a yellow dye image, couplers of, e.g., the acylacetoanilide type or the dibenzoylmethane type are employed. In order to form a magenta dye image, couplers of the pyrazolone, pyrazolobenzimidazole, cyanoacetophenone or indozolone type are generally used. In order to form a cyan dye image, phenolic couplers, e.g., phenols and naphthols, are generally used.
In recent years, it has acquired a greater importance than in the past to enhance image qualities of silver halide photographic materials, particularly those for taking color photographs, as disk cameras and 110-size cameras have been popularized. Especially, improvements in sharpness and granularity are of importance.
It is also well known that couplers can be employed not only for forming dye images, but also for the purpose of releasing photographically useful groups. On the other hand, various compounds capable of releasing photographically useful groups have been used for a wide variety of purposes, respectively, for instance, enhancement of color reproducibility, improvement in granularity, improvement in sharpness, increase in photographic speed, and so on.
Moreover, certain couplers which can release, from their coupling sites, compounds capable of capturing oxidation products of color developing agents have been described, for example, in Japanese Patent Applications (OPI) Nos. 28318/77, 111537/82 and 138636/82, and so on. In detail, Japanese Patent Application (OPI) No. 28318/77 discloses a coupler capable of releasing a so-called competing coupler residue upon reaction with an oxidation product of an aromatic primary amine developing agent. Japanese Patent Application (OPI) No. 111537/82 discloses a coupler illustrated by the following formula: ##STR2## wherein Non-diffusible COUP (A) is a non-diffusible coupling component (A) bonding to the oxygen atom at the position at which a coupling reaction takes place with an oxidation product of a color developing agent to form a colored or colorless compound, and Diffusible COUP (B) is a diffusible coupling componet (B) bonding to Non-diffusible COUP (A) through the oxygen atom in such a manner that it is released upon the coupling reaction between Non-diffusible COUP (A) and the oxidation product and it also reacts with an oxidation product of the color developing agent as a 4-equivalent coupler to form a dye. Japanese Patent Application (OPI) No. 138636/82 discloses a coupler represented by COUP-ED, wherein COUP is a photographic coupler residue capable of forming a dye image by a reaction with an oxidation product of a color developing agent, and ED is a group bonding to the coupling site of COUP and being released from COUP to undergo an oxidation-reduction reaction with an oxidation product of a color developing agent. Such couplers, though employed with the intention of improving granularity or controlling the gradation, do not have much effect, so further improvement on such couplers has been desired. In addition, compounds released from these known couplers to capture oxidation products of developing agents have been found to have not only weak capturing power, but also little diffusibility. Accordingly, they cannot fully achieve the desired improvement in sharpness, and further, cannot produce the interimage effect due to diffusion into other layers.